Astigmatism

Astigmatism is a condition in which one or more surfaces in the eye (usually the cornea or the intra-ocular-lens) refracts the light to two different focals, causing the light rays to produce the image in front and/or behind the retina and not directly on the retina. That is why near and distant objects can appear blurry. Correction with a cylinder lens focusing the light on the retina.